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2023-12-08 01573e231f18eb2d99162747186f59511f56b64d

 kernel/fs/char_dev.c
..
..
@@ -88,21 +88,30 @@
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 /*
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  * Register a single major with a specified minor range.
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  *
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- * If major == 0 this functions will dynamically allocate a major and return
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- * its number.
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+ * If major == 0 this function will dynamically allocate an unused major.
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+ * If major > 0 this function will attempt to reserve the range of minors
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+ * with given major.
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  *
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- * If major > 0 this function will attempt to reserve the passed range of
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- * minors and will return zero on success.
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- *
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- * Returns a -ve errno on failure.
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  */
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 static struct char_device_struct *
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 __register_chrdev_region(unsigned int major, unsigned int baseminor,
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 			   int minorct, const char *name)
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 {
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-	struct char_device_struct *cd, **cp;
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-	int ret = 0;
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+	struct char_device_struct *cd, *curr, *prev = NULL;
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+	int ret;
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 	int i;
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+
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+	if (major >= CHRDEV_MAJOR_MAX) {
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+		pr_err("CHRDEV \"%s\" major requested (%u) is greater than the maximum (%u)\n",
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+		       name, major, CHRDEV_MAJOR_MAX-1);
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+		return ERR_PTR(-EINVAL);
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+	}
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+
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+	if (minorct > MINORMASK + 1 - baseminor) {
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+		pr_err("CHRDEV \"%s\" minor range requested (%u-%u) is out of range of maximum range (%u-%u) for a single major\n",
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+			name, baseminor, baseminor + minorct - 1, 0, MINORMASK);
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+		return ERR_PTR(-EINVAL);
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+	}
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115
 
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 	cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
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 	if (cd == NULL)
..
..
@@ -120,10 +129,21 @@
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 		major = ret;
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 	}
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-	if (major >= CHRDEV_MAJOR_MAX) {
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-		pr_err("CHRDEV \"%s\" major requested (%u) is greater than the maximum (%u)\n",
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-		       name, major, CHRDEV_MAJOR_MAX-1);
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-		ret = -EINVAL;
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+	ret = -EBUSY;
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+	i = major_to_index(major);
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+	for (curr = chrdevs[i]; curr; prev = curr, curr = curr->next) {
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+		if (curr->major < major)
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+			continue;
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+
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+		if (curr->major > major)
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+			break;
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+
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+		if (curr->baseminor + curr->minorct <= baseminor)
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+			continue;
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+
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+		if (curr->baseminor >= baseminor + minorct)
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+			break;
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+
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 		goto out;
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 	}
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..
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@@ -132,43 +152,14 @@
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 	cd->minorct = minorct;
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 	strlcpy(cd->name, name, sizeof(cd->name));
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154
 
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-	i = major_to_index(major);
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-
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-	for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
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-		if ((*cp)->major > major ||
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-		    ((*cp)->major == major &&
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-		     (((*cp)->baseminor >= baseminor) ||
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-		      ((*cp)->baseminor + (*cp)->minorct > baseminor))))
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-			break;
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-
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-	/* Check for overlapping minor ranges.  */
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-	if (*cp && (*cp)->major == major) {
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-		int old_min = (*cp)->baseminor;
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-		int old_max = (*cp)->baseminor + (*cp)->minorct - 1;
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-		int new_min = baseminor;
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-		int new_max = baseminor + minorct - 1;
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-
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-		/* New driver overlaps from the left.  */
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-		if (new_max >= old_min && new_max <= old_max) {
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-			ret = -EBUSY;
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-			goto out;
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-		}
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-
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-		/* New driver overlaps from the right.  */
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-		if (new_min <= old_max && new_min >= old_min) {
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-			ret = -EBUSY;
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-			goto out;
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-		}
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-
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-		if (new_min < old_min && new_max > old_max) {
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-			ret = -EBUSY;
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-			goto out;
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-		}
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-
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+	if (!prev) {
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+		cd->next = curr;
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+		chrdevs[i] = cd;
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+	} else {
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+		cd->next = prev->next;
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+		prev->next = cd;
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 	}
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162
 
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-	cd->next = *cp;
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-	*cp = cd;
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 	mutex_unlock(&chrdevs_lock);
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 	return cd;
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165
 out:
..
..
@@ -492,6 +483,9 @@
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 	p->dev = dev;
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 	p->count = count;
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485
 
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+	if (WARN_ON(dev == WHITEOUT_DEV))
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+		return -EBUSY;
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+
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 	error = kobj_map(cdev_map, dev, count, NULL,
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 			 exact_match, exact_lock, p);
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 	if (error)